Excluse empty-string URLs from icons table

sql/MySQL/6.sql

@@ -30,7 +30,7 @@ create table arsse_icons(
     type text,
     data longblob
 ) character set utf8mb4 collate utf8mb4_unicode_ci;
-insert into arsse_icons(url) select distinct favicon from arsse_feeds where favicon is not null;
+insert into arsse_icons(url) select distinct favicon from arsse_feeds where favicon is not null and favicon <> '';
 alter table arsse_feeds add column icon bigint unsigned;
 alter table arsse_feeds add constraint foreign key (icon) references arsse_icons(id) on delete set null;
 update arsse_feeds as f, arsse_icons as i set f.icon = i.id where f.favicon = i.url;

sql/PostgreSQL/6.sql

@@ -31,7 +31,7 @@ create table arsse_icons(
     type text,
     data bytea
 );
-insert into arsse_icons(url) select distinct favicon from arsse_feeds where favicon is not null;
+insert into arsse_icons(url) select distinct favicon from arsse_feeds where favicon is not null and favicon <> '';
 alter table arsse_feeds add column icon bigint references arsse_icons(id) on delete set null;
 update arsse_feeds as f set icon = i.id from arsse_icons as i where f.favicon = i.url;
 alter table arsse_feeds drop column favicon;

sql/SQLite3/6.sql

@@ -40,7 +40,7 @@ create table arsse_icons(
     type text,                      -- the Content-Type of the icon, if known
     data blob                       -- the binary data of the icon itself
 );
-insert into arsse_icons(url) select distinct favicon from arsse_feeds where favicon is not null;
+insert into arsse_icons(url) select distinct favicon from arsse_feeds where favicon is not null and favicon <> '';
 create table arsse_feeds_new(
 -- newsfeeds, deduplicated
 -- users have subscriptions to these feeds in another table